Data released yesterday (12 March 2010) by NASA indicates that summer (December-February) surface temperatures in the Southern Hemisphere were the warmest on record. The same period in the northern hemisphere (winter) was the fifth warmest on record and globally it was the second warmest December-February on record. In North America there were sharp contrasts: while NOAA reports that the U.S. experienced the 18th coolest winter on record (out of 115 years), Environment Canada says it was the warmest and driest winter on record for Canada.

According to NASA's Goddard Institute for Space Studies (GISS), the temperature anomaly for the Southern Hemisphere for December 2009 through February 2010 was 0.58oC above the 1951-1980 base period, making it the warmest summer on record (since 1880) for the southern hemisphere. The second warmest year on record was 1998, with a temperature anomaly of 0.54oC above the base period. Among those feeling the heat: Western Australia, which experienced the hottest summer on record. (see Australia in Summer [December-February] 2009-10). [Editor's note: Data released by the U.S. National Oceanic and Atmospheric Administration (NOAA) on 15 March 2010 shows that the Southern Hemisphere has just seen its second warmest summer on record (land and ocean combined). Surface temperatures over land were, according to NOAA data, the highest on record for the season. Southern Hemisphere temperatures at the surface for February alone were the highest on record both for land and for the oceans.]

The northern hemisphere meanwhile saw a winter 0.75oC above the 1951-1980 base period, while global surface temperatures were 0.66oC above the base period. The long-term temperature trends globally and for the two hemispheres are similar, showing a substantial warming since 1880.

The contiguous 48 states of the U.S. -- representing just 1.5% of the Earth's surface -- were generally cool relative to much of the rest of the planet for the season. It was the 18th coldest winter on record for the lower-48 states. Winter 2009-2010 was only the second time in 16 years (since the cold winter of 1993-4) that the U.S. has had a winter colder than the long-term mean. The only other colder than normal winter during the 16 year period was the winter of 2000-2001. (see figure below). The trend in the U.S. is towards warmer winters, with temperatures increasing an average of 0.17oF per decade between 1880 and 2010.

For Alaska (not included in the data above), this was the 19th warmest winter on record. Most of the winters during the last three decades have been above the long-term mean and the long term trend (over the period of record starting in 1920) has been towards warmer winters.

The data clearly contradicts the unfounded assertions of climate change denialists. "The bottom line is this: there is no global cooling trend," says the director of NASA GISS, James Hansen a recent essay he wrote with several colleagues (If It’s That Warm, How Come It’s So Damned Cold? [PDF] ). "For the time being, until humanity brings its greenhouse gas emissions under control, we can expect each decade to be warmer than the preceding one."

"`It's beyond shocking,' David Phillips, a senior climatologist with Environment Canada, said Tuesday. Records have been shattered from "coast to coast to coast."

`It is truly a remarkable situation,' says Phillips, noting that he's seen nothing like it in his 40 years of weather watching. He also warns that `the winter that wasn't' may have set the stage for potentially `horrific' water shortages, insect infestations and wildfires this summer."

As the figure below indicates, the temperature departures from normal (also known as anomalies) were large and positive not just in Canada but over most of the Arctic region. Note too the extraordinary warm area stretching roughly from Tibet across the Middle East, North Africa and into the east Atlantic waters off the coast of Africa -- the breeding ground for many Atlantic hurricanes.

"Sea Surface Temperatures (SSTs) in the Atlantic's Main Development Region for hurricanes were at their highest February level on record last month, according to an analysis of historical SST data from the UK Hadley Center. SST data goes back to 1850, though there is much missing data before 1910 and during WWI and WWII. The region between 10°N and 20°N, between the coast of Africa and Central America, is called the Main Development Region (MDR) because virtually all African waves originate in this region. These African waves account for 85% of all Atlantic major hurricanes and 60% of all named storms. When SSTs in the MDR are much above average during hurricane season, a very active season typically results (if there is no El Niño event present.)

Should those water temperature remain elevated well above normal into the hurricane season -- and should the current El Nino in the tropical Pacific fade by the time of the hurricane season (usually 1 June through 30 November) -- some of the key ingredients will be in place for such an active season.